Tau4 Eridani
Tau4 Eridani (τ4 Eridani, τ4 Eri) is a binary star system in the constellation Eridanus. It is visible to the naked eye with an apparent visual magnitude of 3.65. The distance to this star can be estimated using the parallax method, which yields a value of roughly 300 light years.
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Eridanus |
| Right ascension | 03h 19m 31.00224s |
| Declination | −21° 45′ 28.3049″ |
| Apparent magnitude (V) | 3.65 |
| Characteristics | |
| Evolutionary stage | asymptotic giant branch |
| Spectral type | M3/4 III |
| U−B color index | +1.79 |
| B−V color index | +1.61 |
| Variable type | Lb |
| Astrometry | |
| Radial velocity (Rv) | +41.7±0.7 km/s |
| Proper motion (μ) | RA: +51.89 mas/yr Dec.: +32.92 mas/yr |
| Parallax (π) | 10.6153 ± 0.3213 mas |
| Distance | 307 ± 9 ly (94 ± 3 pc) |
| Absolute magnitude (MV) | −0.79 |
| Details | |
| Mass | 1.8±0.3 M☉ |
| Radius | 106 R☉ |
| Luminosity | 1,537 L☉ |
| Temperature | 3,712 K |
| Other designations | |
| Database references | |
| SIMBAD | data |
This is an evolved red giant star currently on the asymptotic giant branch with a stellar classification of M3/4 III. It is a slow irregular variable star of type Lb, undergoing changes in magnitude over the range 3.57−3.72 with a periodicity of 23.8 d. The measured angular diameter of Tau4 Eridani is 10.58±1.00 mas. At its estimated distance, this yields a physical size of about 106 times the radius of the Sun. It shines with 1,537 times the luminosity of the Sun from an outer atmosphere at an effective temperature of 3,712 K.
This is most likely a binary star system. The companion is a magnitude 9.5 star at an angular separation of 5.7″ along a position angle of 291°, as of 2013.